1. Field of the Invention
The present invention relates to a joint body comprising a ceramic member composed of a main body and a projection projected therefrom and a ceramic cylindrical body, and a process for manufacturing the same.
2. Description of Related Art
The present inventors have disclosed a ceramic heater of a specific structure as a heating device for use in a thermal CVD apparatus for producing semiconductors, for example, in the specification of Japanese patent application 301,897/1991. For manufacturing such ceramic heaters, it has become necessary to join a disc-shaped substrate made of silicon nitride ceramic with a tungsten resistor embedded therein and a cylindrical member made of silicon nitride. However, the inventors have found it difficult to join such ceramic members each other in high strength.
For example, the inventors tried to join the above-mentioned disc-shaped substrate with a cylindrical member with an oxide glass, however, it was found that a mechanical strength at a joint portion was low. Moreover, when a heating device comprising such a joint body was placed in an apparatus for producing semiconductors and corrosive gases or gases for forming a semiconductor membrane were fed into the apparatus, there was a possibility of gas leakage from joint portions between the aforementioned disc-shaped substrate and the cylindrical member. Additionally, there are also a possibility of forming cracks at the joint portions during using the heating device repeatedly.
Further, the inventors applied a brazing material between an aluminum nitride member and a ceramic member, and tried to join both the members by heating the brazing material. However, it was found that the joint strength was low, because most of the brazing materials, though they joined well to metal members, hardly wetted the aluminum nitride members, so that they could not join to aluminum nitride members due to poor adhesion or growth of fine gaps. Moreover, when the joint body was placed in the apparatus for producing the semiconductors, the joint body comprising the aluminum nitride members was necessarily exposed to a halogenous corrosive gas atmosphere, particularly to a plasma atmosphere. However, in this case, the corrosive gas entered inside the joint body from the joint portion and deteriorated the joint layer with the consequence that the joint strength of the aluminum nitride joint body was lowered.